The present invention relates to a coupling for metal pipelines and the like.
On metal pipelines electrical interruptions have become a hard-felt necessity, either for technical or safety reasons, as a direct consequence of spontaneous and electrolytic phenomena which affect buried pipelines. Attempts have been made to avoid this phenomena by using suitable coatings on pipelines, and also by inserting insulating joints in order to interrupt the electrical continuity. The joint of one type which is used now has a disc which is embedded in hard insulating material and inserted between two flanges, and the flanges are isolated from the bolts and locking nuts by insulating sleeves and insulating washers. The sealing between the flanges and the insulating disc is obtained by means of rectangular or annular gaskets with their housings on the flanges.
The above mentioned traditional insulating joint has to be positioned within an inspection pit so as to allow for the required maintenance due to inconveniences presented by the joint. In fact, periodic tightening of the nuts is needed, caused by the giving of various components. Frequently sleeves have to be substituted as a result of breakage. Finally, the insulating disc has to be cleaned or replaced periodically due to the shortcircuiting of the joint caused by conductive deposits formed on the internal surface of the disc.